Maximum-demand indicator.



L. T. ROBINSON.

MAXIMUM DEMAND INDICATOR.

APPLIOATION FILED MAY 22, 1913.

Patented NOV. 24, 1914.

Fig. I.

Inventor Lewis T. Rob'nson His fittorney,

25 Witnesses:

ra'rs are:

LEWIS T. ROBINSON, F SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTix'iiC COMPANY, A CORPORATION OF NEW YORK.

MAXIMUM-DEMAND INDICATOR.

Specification of Letters Patent.

Patented Nov. 24, 1914.

Application filed May 22, 1913. Serial No. 769,168.

' Demand Indicators, of which the following is a specification.

My invention relates to maximum demand indicating instruments, and in particular to instruments which indicate the maximum demand made by an electrical installation upon a central generating station or other source of electric energy supply.

A modern problem of considerable importance in the distribution of electrical energy to individual consumers is to determine the tariff rate which slfould be charged each consumer for the energy he uses. One method of determining this tarifl rate for electrical energy which is regarded with considerable favor consists in basing the rate upon the maximum demand made by the consumers installation upon the central generating plant. A determination or measurement of the maximum demand is obviously necessary where this method of charging is in vogue. Contracts in which the maximum demand is made the basis for the tariil' rate usually provide a certain agreed rate when the maximum demand is between predetermined limits, and a diii'er- 'ent rate. when the maximum demand is between other limits. \Vhere this method of determining the tariil rate is employed, an instrument is required which will accurately measure and record the greatest or maximum demand made by the installation, and

in a manner satisfactory to the consumer and to the central station management.

My invention contemplates a novel construction of instrument particularly adapted to measure the -maximum demand and possessing characteristics which render such measurement acceptable to both the consumer and the central station.

The object of my invention is to provide a novel and improved construction of maximum demand indicator.

More specifically, the object of my inven tion is to provide a simple, inexpensive and compact construction of maximum demand indicator which can be economically supplied to consumers using only small quantities of energy.

A further object of my invention'is to provide a novel construction of maximum demand indicator whose operative elements can be actuated entirely by the field coils of a *attmeter, and whose indications are of sutiicicnt accuracy for all practical purposes.

The novel and patentable features Which I believe to be characteristic of my invention are indicated in the claims appended hereto.

The construction and mode otoperation of a. maximum demand indicator embodying my invention will be understood by reference to the following description taken in connection with the accompanying drawings, in which Figure 1v is a diagrammatic view in perspective of my novel and improved maximum demand indicator embodied in a Wattmeter of the induction type, and operatively connected to an electrical installation, and Fig. 2 is an elevation of a portion of my improved indicator showing the scale of the integrating watthour meter and the maximum demand scale.

lcierring to Fig. 1 of the drawings, there is shown a system of distribution comprising conductors 5 supplying electric energy to translating devices 6. A watthour meter of the induction type is operatively connected to the system in the usual manner for the purpose of integrating and registering the total quantity of energy consumed in the translating devices. The induction wattmeter comprises the usual series coil 7 and potential coils S which produce a shifting magnetic field proportional to the instantaneous rate of consumption of energy in the well understood manner.

Two rotatable disk armatures are located within the influence of the magnetic. field produced by the coils '7 and 8. One of these disk armatures this arranged as the rotatable element of a watthour meter. Permanent magnets 10 are mounted in operative relation to the disk armature 9, so that the revolutions of the armature are directly proportional to the watthour-s of energy consunied in the translating devices. The second armature 11 is arranged as the movable element of an indicating wattmeter. Permanent magnets 12 are operatively associated with the indicating Wattmeter armature 11.

A shaft 13 is rigidly secured to the indieating Wattmeter armature 11 and carries at its upper end agear member 14. The gear member 1 1 operatively engages a gear 15 rigidly secured to a shaft 16. A control spring 17 is operatively connected at one end to the shaft 16 and at the other end to a fixed part 18 of the instrument. The control spring is designed to render the movement of the disk armature 11 a measure of the strength of the magnetic field, and thus a measure of the instantaneous rate of consumntion of energy.

An L shaped contact member 19 is rigidly secured to the shaft 16, and, due to the action of the control spring 17. normally en gages with a fixed stop 20 when no energy is being consumed in the translating 'dcvices. The engagement of the contact mem ber'19 with the fixed stop 20 determines the zero or initial position of the ftl'll'lfltlll'e of the indicating Wattmeter element. hen energy is being consumed in the translating devices, the contact member is moved by the shaft 16 and alv-Iays occupies a position Whose distance from the initial position, determined by the iixed stop 20, is a measure of the instantaneous rate of consumption of energy in the installation. It will thus be seen that the movable contact member 19 corresponds to the indicating pointer of'an ordinary indicating wattmeter.

A shaft 21. is rigidly secured to the rotatable disk 9 of the watthour meter element. The shaft 21 drives, through gearing 22, the usual registering mechanism of the meter. This mechanism has been 1 of the drawing, but the reg-is or dial .20 operatively connected to the shaft and gearing 22, is shown in Fig. of the drawings.

The rotatable shaft 21 of the watthour meter is arr-an; to drive a shaitfllby means of the gearing and intermcshing gears 25 and 2(5. The gear 26 performs the function of an actuator to drive a. non-return pointer 27 across a suitable scale 28. This is acconuplishe'l by means of a pin '29 secured to the actuator gear 26 and arranged to engage the non-return pointer 27. The zero position of the non-return pointer is determined by a fixed pin 30, shown in F 2 of the drawings.

One end of the shaft 2% is pivoted at 31 omitted in l to a fixed portion of the instrument, while the other end of this shaft is pivoted at 32 to one end of a lever arm The lever arm is fulcrumed about a pin 34; and is normally maintained. bymeans of the spring 35, in such a position that gear 25 operatively engages the actuator gear 2 3. The armature 36 of apair of coiiperating electro- .g1agnets37 is secured to the other end of the lever arm 33. The arrangement of the I varmature 36 and lever arm' 33, is such that When the electromagnet 37 is energized the pivot 32 of shaft 24: is elevated and the ac tuator 26 is disconnected from operative engagement with the watthour meter driven gear 25. r

An L shaped contact member 38 is rigidly secured to the shaft 2 1 and is accordingly.

moved when the shaft 24 is driven by the watthour meter. The contact portion of the contact member 38 is arranged to move in substantially the same path as the. contact portion of the contact member 19. If the zero or initial position of the contact member 38 is substantially the same as that of the contact memb r 19. the distance that the contact member 38 moves from its initial position to engagement with the contact member 1 is a measure of the instantaneous rate of consumption of energy at the instant of contact bcti'vcen these members.

A control spring 39 is operatively secured between the shaft 24 and a fixed part of the instrument, and tends to return the actuator 2-6 to an initial position when the operative connection between the actuator and the watthour meter is interrupted. This initial position is determined by a weight 40 which engages with a spring member 41, whosev dmvnward movement is limited by a fixed stop 42.

One terminal of the winding of electromagnet 37 is connected by conductor 13 to one side of the distribution system 5. The other terminal of the winding of the electromagnet is connected by conductord to the shaft 24. The shaft 16 is connected by conductor 15 to the other side of the distribution system 5. lVhen contact member 38 on gages with contact member 19, the electric circuittlu'ough the electromagnet is completed and the magnet is energized. The armature 31.7 is thereby attracted, and the actuator-26 raised from engagement with gear A fixed auxiliary contact 4:6 is electrically connected to the shaft 24. and a cooperating movable contact 47 is electrically connected to the shaft 16. The auxiliary contacts 4-6 and 17 are thus arranged in shunt relation to the main movable contacts 19 and'38. The movable auxiliary contact 41-7 is mounted on the spring member 47-1, and the action of this spring member tends to maintain the auxiliary contacts in engagement. \Vhen the weight 40 rests upon the spring member 11 the engagement of these contacts is 'broken. Furthermore, when the clectromagnet 37 is deenergized, a pin 48, secured to the lever 33, is arranged to cooperate with the spring member 41 and hold the contacts 46 and -17 disengaged.

The operation of my improved n'xax'imum demand indicator is as follows: \Vhen electric energy is being consumed in the translating devices 6, a shifting magnetic field atlases will be produced by the field coils 7 and 8, .resulting in rotation of the watthour meter armature 9 and a turning of the indicating watthour armature 11 until its torque is counter-balanced by the torque of the control spring 17. The movable contact member 19 will, therefore, take up a position whose distance from the initial position of the member is a-measure of the instantaneous rate of consumption of energy in the translating devices. The movable contact mem- 'ber 38 will-be driven by the watthour meter armature 9, gearing 22, gear and actuator 26 toward the contact member 19. llVhen the movable contact member 38 engages with contact member19, it will have moved from its initial position a distance which is a measure of the instantaneous rate of consumption of energy at the moment of engagement of the contact members. When the contact members engage, the electromagnet 37 is energized and the actuator 26 is raised from operative connection with the gear 25.

At the same time the pin 48 is raised, and the auxiliary contacts 46 and 4:7 come into engagement, due to the action of the spring member 421- The actuator is now free to return to its initial position under the influence of the spring 39. The instant before the actuator reaches its initial position, the Weight 40 falls upon the spring member 41 and disengages the auxiliary contacts 46 and 47. The electromagnet 37 is thereby deenergized and the actuator drops into operative engagement with the gear 25. At the same time, pin 48 engages with the spring member 41 and maintains the auxiliary contacts disengaged.

It will be observed that as soon as the actuator starts to return to its initial position the main contact members 38 and 19 are disengaged, and hence it is necessary to provide the auxiliary contacts 46 and L7 to maintain the electromagnet energized, and consequently the actuator 26 operatively disconnected from the gear 25 until the actuator has returned to its initial position. The pin 29 of the actuator engages with the non-return pointer 27 and moves this pointer across the scale 28. The pointer will therefore, indicate the maximum movement of the actuator from its initial position to the position of engagement of the contact members 38 and 19.

When the translating devices 6 are cut out of circuit no energy is being consumed or metered and consequently the indicating wattmeter m niature 11 is returned to its initial position by the spring 17 The contact member 19 then moves toward the contact member 38 and when these contacts engage the actuator is'returned to its initial position as hereinbefore described. The initial or zero position of the contact member 38 is such that this member is slightly return to their initial positions as soon as the consumption of energy in the translating devices is interrupted. This is a particularly important advantage of my improved maximum demand. indicator, as the indicator is always in readiness to begin a measurement of the demand as soon as the consumption of energy begins in the translating devices. Thusthe beginning of an interval of measurement of demand is always coincident with the beginning of the consumption of energy.

I have hereinbefore stated that the movable contact member 38 and the actuator 26 are returned to their respective initial positions when the distance these members have moved from their initial positions is a measure of the instantaneous rate of consumption of energy. This condition is obviously fulfilled only when the initial positions of the contact members 19 and 38 are substantially the same, as shown in the preferred embodiment of my invention herein illustrated. It will be evident to those skilled in the art that under certain conditions it may not be desirable to have the initial positions ot these contact members substantially the same. F or example, the initial position of the movable contact member 38 may, under certain circumstances. be some distance behind or below the initial position of the movable contact member 19. In any case the distance the movable contact member 38 moves from its initial position before engaging with the contact member 19 will be some predetermined and definite function of the instantaneous distance of the contact member 19 from its initial position. Tn other words when the actuator 26 occupies a position with respect to a suitable scale of reference, as for example the scale 28, which is a measure of the rate of consumption of energy. or some predetermined function thereof, at that particular instant, the operative connection between the actuator and the watthour meter element will be interrupted, and the actuator returned to its initial position. I

The measurements obtained with my maximum demand indicator are in sub stance periodical measurements of the instantaneous rate of energy consumption. In other words, I btain measurements of the rate of consumption of energy at par ticular instants- By the improved construction of my indicator these measurements are made in such a manner that the consumption vof energy must continue at the rate recorded for an appreciable and sufiicient interval of time before a measurement of such rate of energy consumption is obtained. A permanent indication is obtained of the maximum rate of energy con sumption so measured.

The time interval between the measurements of demand in my indicator are of secondary in'iportance and the only prerequisite in regard to this interval is that it be of sufiicient duration to insure a measurement of demand which is fair to the consumer and acceptable to the central generating station. The time intervals between the interruptions of the operative connection of the actuator and the watthour meter element, and hence the time intervals between measurements of demand, will be equal if the rate of consumption of energy remains uniform. Furthermore, if the rate of consumption of energy remains uniform while the actuator is moving from its initial posi- Ttion to engagement with the movable member of the indicating wattmeter element, the time intervals will be equal, regardless of the rate of consumption of energy during each separate interval. Such conditions, however, are not at all likely to prevail in actual practice, and the time interval of my imlicator is therefore, indefinite. As previously mentioned, however, the real function of the time interval is to give the indicator a time lag so that the consumer will not be penalized for temporary overloads, such as short circuits.

My maximum demand indicator measures the instantaneous rate of consumption of energy in such a manner that this rate must continue for an appreciable length of time before the i'naisurement will be made. It will accordingly be evident that in some cases the return of the actuator :26 to an initial position each time that the movable contact members 38 and 15) engage may be unnecessary, since it is only desired to interrupt the n'iovement of the. actuator 26 when it occupies a position with respect to the indicating elements of the instrument which is a measure of the instantaneous rate. of consunn tion of energy.

it will be observed from the foregoing description that I have provided a construction of maximum demand indicator which simple, compact and inexpensive to manufacture. The instument is, furthermore, of suilicicnt accuracy to meet all practical operative requirements, and is acceptable to both the consumer and the central generating station. All of the operative elements of the indicator are actuated by the field coils of the induction wattineter. By this construction the constant speed clockwork mechanism which has heretofore characterized nearly all practical maximum demand indicators can be dispensed with, and thus. the cost of the indicator materially reduced. The instrument can, therefore, be manufactured at such a cost as to permit its use in installations where the consumption of energy is too small to warrant the use of the more expensive types of demand apparatus.

Numerous modifications in the details of construction of my improved maximum demand indicator will be evident to those skilled in the art. While I have described as the preferred embodiment of my invention an instrument of the induction type having all of its operative elements actuated by thesame field coils, it Will-be obvious that my invention is not limited either to an instrument of this particular type or to an instrument in which the watthour meter element and the wattmeter element are actuatcd by the same field coils. I do not, therefore, desire to be limited to the specific construction which I have herein described and illustrated, and I aim by the terms of the appended claims to cover all modifications which are within the spirit and scope of my invention.

lVhat I claim as new and desire to secure by Letters Patent of the United States, is:

1. A maximum demand indicator .com-' prising in combination a watthour meter element, anindicating wattmeter element adapted to always occupy a position which is a measure of the instantaneous rate of consumption of energy, a movable member adapted to be actuated by said watthour meter element, means cooperating with said indicating wattmeter element for interrupting the movement of said movable member when said member occupies a position with respect to a suitable reference scale which is a measure of the instantaneous rate of consumption of energy, and means for indicating the maximum movement of said movable member.- I

A maximum demand indicator comprising in combination a watthour meter having field coils'and a rotatable armature, an indicating wattmeter arr. ature pivotally mounted in the magnetic field of said coils, a control spring operatively connected to said indicating wattmeter armature to render its movement a measure of the strengt of the magnetic field, a movable member adapted to be actuated by said watthour meter armature, means cooperating with said indicating wattmetcr armature for interrupting the movement of said movable member when said member occupies a position with respect to a suitable reference scale which is a measure of the instantaneous rate of consumption of energy, and means for indicating the maximum movement of said movable member.

3. A maximum demand .-indicator comprising in combination a Watthour meter element, an indicating wattmeter element adapted to always occupy a position which is a measure of the instantaneous rate of consumption of energy, a movable member having an initial position and adapted to be actuated by said watthour meter element, means coiiperating with said indicating wattmeter element whereby said movable member is returned to its initial position when said member occupies a position with respect to a suitable reference scale which is a measure of the instantaneous rate or" consumption of energy, and means for indicating the maximum movement of said movable member.

4. A maximum demand indicator comprising in combination a watthour meter having field coils and a rotatable armature, an indicating wattmeter armature pivotally mounted in the magnetic field of said coils, a control spring operatively connected to said indicating wattmeter armature to render its movement a measure of the strength of the magnetic field, a movable member having an initial position and adapted to be actuated by said watthour meter armature, means cooperating with said indicating wattmeter armature whereby said movable member is returned to its initial position when said member occupies a position with respect to a suitable reference scale which is a measure of the instantaneous rate of corn sumption of energy, and means for indicating the maximum movement of said movable member.

5. A maximum demand indicator comprising in combination a watthour meter element, an indicating wattmeter element having an initial position and adapted to always occupy a position Whose distance from said initial position is a measure of the instantaneous rate of consumption of energy, a movable member having an initial position and adapted to be ac uated by sail watthour meter element, me s for interrupting the movement of said movable memher when the distance said member has moved from its initial position is a predetermined function of the instantaneous distance of said indicating wattmeter element from its initial position, and means for indicating the maximum movement of said movable member.

6. A maximum demand indicator comprising in combination a watthour meter element, an indicating wattmeter element having an initial position and adapted to alwayoccupy a position whose distance from said initial position is a measure of the instantaneous rate of consumption of energy, a movable member having an initial position and adapted to be actuated by said watthourmetcr element, means for rctui ing said movable member to its initial posi- 7. A maximum demand indicator com-.

prising in combination a watthour meter having a rotatable shaft, a movable member having an initial position, means for operatively connecting said rotatable shaft to said movable member, means for interrupting the operative connection between said shaft and said member when the member 00- cupies a position with respect to a suitable rel'erence scale which is a measure of the instantaneous rate of consumption of energy, means for returning said movable member to its initial position each time the operative connection between said shaft and said member is interrupted, means for maintaining said shaft and said member operatively disconnected while the member is returning to its initial position, and means for indicating the maximummovement of said member.

8. A maximum demand indicator comprising in combination a watthour meter having field coils and a rotatable armature, an indicating wattmeter armature pivotally mounted in the magnetic field of said coils, a control spring operatively connected to said indicating wattmeter armature to render its movement a measure of the strength of the magnetic field, a movable member having an initial position, means for operatively connecting said wattmeter armature to said movable member, means cooperating with said indicating wattmeter armature for interrupting the operative connection between said watthour meter armature and said member when the member occupies a position with respect to a suitable reference scale which is a measure of the instantaneous rate of consumption of energy, means for returning said movable member to its initial position each time the operative connection between said watthour meter armature and said member is interrupted, means for maintaining said watthour meter armature and said member operatively disconnected while the member is returning to its initial position, and means for indicating the maximum movement of said movable member.

9. A maximum demand indicator-comprising in combination a watthour meter having a rotatable shaft, a movable memher having an initial position, means for operatively connecting said rotatable shaft to said movable member, means for interrupting the operative connection between said shaft and said member when the distance the member has moved from its initial position is substantially a measure of the instantaneous rate of consumption of energy, means for returning said movable member to its initial position each time the operative connection between said shaft and said member is interrupted, means for maintaining said shaft and said member operatively disconnected while the member is returning to its initial position, and means for indicating the maximum movement of said member.

10. A maximum demand indicator comprising in combination a watthour meter element and an indicating wattmeter element, a movable member having an initial position, means for operatively connecting said watthour meter element to said movable member, means cooperating with said indicating wattmeter element for interrupting the operative connection between said watthour meter element and said movable member when the distance the member has moved from its initial position is substantially a measure of the instantaneous rate of consumption of energy, means for returning said movable member to its initial position each time. the operative connection between the Watthour meter element and the member is interrupted, means for maintain ing said watthour meter element and said member operatively disconnected while the member is returning to its initial position, and means for indicating the maximum movement of said movable member. 11. A maximum demand indicator comprising in combination a Watthour meter having field coils and a rotatable armature, an indicating wattmeter armature pivotally mounted. in the magnetic field of said coils, a control spring operatively connected to said indicating wattlneter armature to render its movement a measure of the strength of the magnetic field, a movable member having an initial position, means actuated by said watthonr meter armature for driving said movable member, means cooperating with said indicating Wattmeter armature whereby said movable member is returned to its initial position when the distance the member has moved from its initial position is substantially a measure of the instantaneous rate of consumption of enorgy, and means for indicating themaximum movement of said movable member.

12. A maximum demand indicator comprising in conibination a watthour meter having field coils and a rotatable armature, an indicating uattmeter armature pivotally mounted in the magnetic field of said coils, a control spring oporatively connected to said indicating wattmeter armature to render its movement proportional to the strcngthiof the magnetic field, a movable member having an initialposition, means for operatively connecting said watthour meter armature to said movable member,- means cooperating with said indicating wattmeter armature for interrupting the operative connection between said Watthour meter armature and said member When the distance the member has moved from its initial position is substantially a measure of the instantaneous rate of consumption of energy, means for returning said movable member to its initial position each time the operative connection between said Watthour meter armature and said member is interrupted, means for maintaining said wattliour meter armature and said member 0peratively disconnected while; the member is returning to its initial position, and means for indicating the maximum movement of said movable member.

13. A maximum demand indicator comprising in combination a Watthour meter having field coils and a rotatable armature, an indicating wattmeter armature .p'ivotally m unted in the magnetic field of said coils, a control spring operatively connected to said indicating Wattmeter armature to render its movement a me sure of the strength of the magnetic field, a movable member having an initial position, means actuated by said \vatthour meter armature for driving said movable member, means 00- 9 operating with said indicating Wattmeter armature for interrupting the movement of said movable member when the distance the member has moved from its initial position is substantially a measure of the instantaneous rate of consumption of energy, and

'means for indicating the maximum movement of said movable member.

14. A maximum demand indicator comprising in combination a watthour meter having field coils and a rotatable armature, an indicating wattmeter armature pivotally mounted in the magnetic field of said coils, a control spring operatively connected to said wattmeter armature to render its movement a measure of the strength of the magnetic field, a movable member having an initial position, means actuated by said rotatable uatthour meter armature for driving said movable member, means for interru ting the movement of said movable mem er when the extent of its movement from its initial position is at any instant a predetermined function of the extent of movement of said indicating wattmeter armature from its initial position, and means for indicating the maximum movement of said movable member. 1

15. A maximum demand indicator comprisin in combination an electric meter having field coils and a rotatable armature, an armature member pivotally mounted in the magncctic field of sa d coils, a spring operatively connected to said a rmatu re member and opposing its movement in response to the influence nuance of said'coils a movable member having an initial position and adapted to be driven by said rotatable armature, means cobperating with said armature member for causing said movable member to be returned to its initial eating wattmeter element and adapted toalways occupy a position Whose distance from said initial position is a measure of the instantaneous rate of consumption of energy, a second movable member having an initial position and adapted to be actuated by said watthour meter element, means for interrupting the movement of said second movable member when said second movable member has moved from its initial position a distance substantially equal to the instantaneous distance of said first-mentioned movable member from its initial position, and means for indicating the maximum movement of said second movable member.

17. A maximum demand indicator comprising in combination a watthour meter having field coils and a rotatable armature, an indicating Wattmeter armature pivotally mounted in the magnetic field of said coils, a control spring operatively connected to said wattmeter armature to render its movea measure of the strength of the magnetic field, movable member adapted to be actuated by the indicating wattmeter armature. a second movable member having an initial position and adapted to move in substantially the same path as the'first-mentioned movable member, means actuated by said rotatable watthour meter armature for roving said second movable member, means for interrupting the movement of said second movable member when said second movable 1 nbc engages with said first-mentioned movable member, and means for in (heating the maximum, movement of said second movable member.

18. A maximum demand indicator comprising in combination a waithour meter element and an indicatingswattmeter element, a movable member having an initial position operatively connected to saidindieating wattmetcr element and adapted to always occupy a position whose distance from said initial position is a measure of the instantaneous rate of consumption of energy, a (fond movable member having an initial p on and adapted to be actuated by said watthour meter element, means I'or returning said second vabie member to its initial position when said second movable member has moved from its initial position a distance substantially equal to the instantaneous distance of said first-mentioned movable member from its initial position, and means for indicating the maximum movement of said second movable member; v

19. A maximum demand indicator comprising in combination a watthour meter element and an indicating Wattmeter element, a movable member having an initial position operatively connected to said indicating wattmeter element and adapted to always occupy a position Whose distance from said initial position is a measure of the instantaneous rate of consumption of energy, a second movable member having an initial position and adapted to move in sub stantially the same path as the first-mom 35 tioned movable member, means actuated by the watthour meter element for moving said 1 second movable member, means for returning said second movable member to its initial position when it engages with said firstmentioned movable member, and means for indicating the maximum movement of S316. second movable member.

20. A maximum demand indicator'com- P151110 in combination a watthour meter 615 element and an indicating wattmeter element, a movable member having an initial position operatively connected to said indie? eating wattmeter element and adapted tog always occupy a position whose distance cev from said initial position is a measure of the instantaneous rate of consumption of energy, a second movable member having an initial position, means for operatively connecting said watthour meter element to said second movable member, means for interru'pting the operative connection between said watthour meter element and said second member when the distance the second member has moved from its initial position is substantially equal to the instantaneous distance of said first-mentioned member from its initial position, meansfor returning said second movable member to its ini tial position each time'the operative con- 13.5

nection between the Watthour meter element and the second movable member is interrupted, and means for indicating the maximum movement of said second movable member. v

21. A maximum demand indicator comprising in combination a -watthonr meter having a rotatable shaft, a movable member having an initial position, means for operatively connecting said rotatable shaft to said movable member, an electric circuit ineluding an electromagnet, a movable armature for said electromagnet adapted by its movement to interrupt the operative connection between said rotatable shaft and 3-;

said movable member, means for changing the electrical condition of the circuit when said member occupies a position with respect to a suitable reference scale which is a measure of the instantaneous rate of con sumption of energy, means for returning said member to its initial position each time the operative connection between said shaft and said member is interrupted, and means for indicating the maximum movement of said movable member.

22. A maximum demand indicator comprising in combination a 'watthour meter element and an indicating Wattmeter elemerit, a movable member having an initial position operatively connected to said wattmeter element and adapted to always occupy a position whose distance from said initial position is a measure of the instantaneous rate of consumption of energy, second movable member having an initial position, means for operatively connecting said watthour meter element to said second movable member, an electric circuit including an electromagnet, a movable armature for said electromagnet adapted by its movement to interrupt the operative connection between said watthour meter element and said second movable member, means for changing the electrical condition of the circuit when the distance the second member has moved from its initial position is a predetermined function of the instantaneous distance of said first-mentioned movable member from its initial position, means for returning said second movable member to its initial position each time the operative connection between said watthour meter element and said second movable member is interrupted, and means for indicating the maximum movement of the second movable member.

28. A maximum demand indicator comprising in combination a watthour meter having field coils and a rotatable armature, an indicating.wattmeter armature pivotally mounted in two magnetic field of said coils, a control spring operatively connected to said wattmeter armature to render its movement a measure of the strength of the magnetic field, a movable member having an initial position, means actuated by said rotatable watthour meter armature for driving said movable member, means for returning said movable member to its initial. position when the extent of its movement from its initial position is at any instant a predetermined function of the extent of movement of said indicating wattmeter armature from its initial position, and means for indicating the maximum movement of said movable member.

24. A maximum demand indicator comprising in combination a watthour meter having field coils and a rotatable armature, an indicating wattmeter armature pivotally .said wattmeter armature to render mounted in the magnetic'deld of said coils, a control spring operatively connected to its movement a measure of the strength of the magnetic field, a movable member adapted to be actuated by the indicating wattmeter armature, a second movable member having an initial position and adapted to move in substantially the same path as the firstmentioned movable member, means actuated by said rotatable armature for moving said second movable member, means for returning said second movable member to its initial position when it engages with said firstmentioned movable member, and means for indicating the maximum movement of said second movable member.

i. A maximum. demand indicator comprising in combination a watthour meter element and an indicating wattmeter element, an actuator having an initial position and adapted to be operatively connected to the watth our meter element, a movable member having an initial position operatively connected to said wattmeter element and adapted to always occupy a position whose distance from said initial position is a measure of the instantaneous rate of consump tion of energy, means for interrupting the operative connection between the actuator and the watthour meter element when the distance the actuator has moved from its initial position is a predetermined function of the instantaneous distance of said indicating Wattmcter element from its initial position, means for returning said actuator to its initial position when the operative con nection between the actuator and the Watthour meter element is interrupted, means for maintaining said actuator and said watthour meter element operatively disconnected until the actuator has returned to its ini-' tial position, and means for indicating the maximum movement of said actuator:

26. A maximum demand'indicator comprising in combination a Watthour meter element and an indicating wattmeter element, an actuator having an initial position and adapted to be operatively connected to the watthonr meter element, an electric circuit including an ,electromagnet, a movable armature for said electromagnet, means opcratively connected to said armature whereby a movement of the armature interrupts the operative connection between the actuator and the watthour meter element, movable contacts in said electric circuit, one of said movable contacts being operatively con nected to said indicating wattmeter element and the other movable contact being operativelv connected to the wattbour meter element, meal for returning said actuator to its initial position when the operative con; nection between the :actuator and the watthour meter element is interrupted, and means for indicating the maximum movement of said actuator.

27. A maximum demand indicator comprising in combination a 'Watthour meter having field coils and a rotatable armature, an indicating Wattmeter armature pivotally mounted in the magnetic field of said coils, a control spring operatively connected to said indicating Wattmeter armature to render its movement a measure of the strength of the magnetic field, an actuator having an initial position and adapted to be operatively connected to the watthour meter armature an electric circuit including an electromagnet, a movable armature for said electromagnet, means operativel connected to said armature whereby a movement of the armature interrupts the operative connection between said actuator and said watthour meter armature, movable contacts in said electric circuit, one of said movable contacts being operatively connected to the indicating \vattmeter armature and the other contact being operatively connected to the watthourineter armature, means for returning said actuator to its initial position when the operative connection between the actuator and the Watthour meter armature is interrupted, and a non-return pointer adapted to be moved by said actuator.

28. A maxim demand indicator comprising in coniiniiz: on' a Watthour vmeter having field coils a: a rotatable armature, an indicating \vai ater armature pivotally mounted in the naignetic field of said coils, a control spring operatively connected to said indicating Wattmeter armature to render its movement a measure of the strength of the magnetic field, an actuator having an initial position and adapted to be operatively connected to said Watth ur meter armature, an electric circuit including an electromagnet, a movable armature forsaid electromagnet operatively connected to said actuator and adapted by its movement to interrupt the operative connection be tween the actuator and the Watthour meter armature when the electromagnet is energized, a pair of cooperating movable contacts in said electric circuit, one of said contacts being operatively connected to said indicating \vattmeter armature and the other contact being operatively connected to said \vatthour meter armature, a pair of cooperating auxiliary contacts, in shunt relation to said first mentioned contacts, means for returning said actuator to its initial position when said first-mentioned contacts engage with each other and the operative connection between said actuator and said watthour meter armature is interrupted, means for closing said auxiliary contacts When said first-mentioned contacts engage and for maintaining the auxiliary contacts closed until. said actuator has returned to its initial position, and a non-return pointer adapted to be moved by said actuator.

In witness whereof, I have hereunto set my hand this 20th day of May 1913.-

LEWIS T. ROBINSON.

' W'itnesses:

Baum-mm B. HULL, HELEN Onronn. 

